The long-term goals of this project are to develop general, high-throughput methods to identify, evolve, and characterize small molecule and protein inhibitors and activators of ion channel function. Ion channels are coveted drug targets. As membrane proteins, they are readily accessible to applied extracellular compounds and their modulation brings about rapid changes in the signaling properties of excitable cells in the heart and brain. However, as membrane proteins, they also reside beyond many of the well-established approaches for inhibitor and activator development that require purified material. Consequently, many lack any significant pharmacologies. This problem leads to a large gap in our ability to connect ion channel genes with in vivo function. Unraveling the physiological and biophysical functions of ion channels demands new tools that allow the manipulation of a given type of channel's action in a variety of settings. To address this issue, we are using novel genetic selection approaches to develop activators and inhibitors of two classes of potassium channels that lack robust pharmacologies, inwardly rectifying and Two-P potassium channels. These channels are thought to play central roles in neurotransmitter regulation of neuronal and cardiac excitability but precise delineation of their functions awaits reagents that can specifically activate or block their function. We are pursuing genetic selections for both small molecule and peptides. Our approach is multidisciplinary and includes genetics, biochemistry, electrophysiology, and structural biology to dissect and characterize the modes of action of selected modulators. Because of their important roles in human physiology, ion channels are the targets for drugs to treat a wide range of diseases including epilepsy, cardiac arrhythmias, stroke, hypertension, diabetes, and memory loss. In addition to being intended drug targets, a number of ion channels, particularly cardiac ion channels, are unusually susceptible to unwanted cross-reactivity. This issue impedes the progress of many drug development trials. Thus, developing an understanding of how small molecules act on ion channel function as well as developing high-throughput methods for assaying compounds that lead to ion channel block should not only provide powerful tools for dissecting channel mechanism and function but should aid in the development of new therapeutic agents for a range of human diseases.